The primary objective of this project is to develop new agents for the treatment of childhood cancers with an emphasis on a more rational, targeted approach of drug development based on the current understanding of the molecular pathogenesis of human cancers. New molecularly targeted agents that are undergoing clinical development for adult cancers will be applied to childhood cancers based on the mechanism of action of the drug and the importance of the target in childhood cancers. In addition, novel cytotoxic agents are undergoing clinical evaluation. This work is performed through the Pharmacology and Experimental Therapeutics (P&amp;ET) Section of the NCI POB. Dr. Frank Balis, who was the Head of this Section for many years, left the NCI in June 2009, and since then I have resumed leadership of P&amp;ET Section. Examples of clinical trials ongoing and in development include: 1) The development of the raf kinase and receptor tyrosine kinase inhibitor sorafenib for children with refractory cancers and leukemias. A phase I trial of sorafenib conducted by Childrens Oncology Group (COG) Phase I Consortium with myself serving as protocol chair is close to completion, and we are proposing a phase II trial for select solid tumor strata to be performed as a COG wide study. Simultaneously sorafenib is developed for neurofibromatosis type 1 (NF1) related tumors (see project 1). 2) The mTOR pathway is involved in the progression of human cancers and neurofibromatosis type 1 (NF1) related tumors, and clinical trials with mTOR inhibitors are ongoing, and will be pursued for both patient populations. For example, a multi-institutional clinical trial for patients with refractory sporadic or NF1 related malignant peripheral nerve sheath tumors (MPNST) with the mTOR inhibitor RAD001 alone and in combination with the angiogenesis inhibitor bevacizumab will soon open for enrollment. This trial is receiving funding through a Department of Defense Clinical Trial Award to the Trial PI B. Widemann). 3) In addition, we are pursuing the clinical development of novel cytotoxic agents for children and young adults with refractory cancers. We are currently leading a multi-institutional phase II trial of neoadjuvant chemotherapy for patients with high-grade, unresectable, chemotherapy nave malignant peripheral nerve sheath tumors (MPNST). MPNSTs are aggressive soft tissue sarcomas and are associated with poor outcome, particularly in individuals with NF1 (see project 1). We also evaluated the epothilone B analog ixabepilone (BMS-247550), an antitubulin agent, which inhibits tubulin depolymerization. A single institution phase I trial within the NCI was completed, and followed by a COG wide phase II trial, which was also recently completed. A phase I clinical trial of satraplatin, a novel orally bioavailable platinum agent, is currently in development as a single institution phase I trial. Satraplatin demonstrates antitumor activity in preclinical models including cisplatin resistant models, and has shown activity in adult trials for several solid malignancies including prostate cancer. The dose-limiting toxicity of satraplatin is myelosuppression. Neurotoxicity and renal toxicity, which are associated with cisplatin and carboplatin, have not been described in patients receiving satraplatin. The lack of these toxicities and the preclinical and clinical activity provide a strong rationale for the development of satraplatin for children with refractory cancers. The pharmacokinetics and pharmacodynamics of drugs in clinical development will be studied and compared to results in adults.